This invention relates to various methods of fabrication of gamma camera plate assemblies having one or more crystals and with improved energy resolution.
A gamma camera plate assembly made by using the prior art process consists of a thick glass plate that serves as carrier for the crystal. The crystal is coupled to the glass plate using an optical cement, a hydroformed aluminum pan that houses the crystal and the glass and a steel or aluminum flange that houses the pan with the crystal and the glass. The thickness of the glass plate has to be capable to carry the crystal. Glass plates having excellent homogeneity, parallel planes and polished on both sides, over half an inch thick are used commonly. The homogeneity of the glass is of extreme importance to eliminate non-even absorption, light scattering, diffraction and loss due to total reflection in the glass plate. Also, a glass plate of thickness and dimensions slightly larger in respect to the crystal is rather heavy. The thickness of the glass plate causes the distance between the crystal and the photomultipliers not to be at its optimum, thus causing degradation in the energy resolution. To prevent sliding and other plate movements the optical cement is of a rather permanent nature, and any plate assembly repair (usually re-polishing of the back side of the crystal exposed to degradation) is either nearly impossible or very difficult even for very skilled persons.